In some communication systems, inter-symbol interference may occur when switching between modulation schemes. For example, in a Global System for Mobile communication (GSM) network implementing Enhanced Data rate for GSM Evolution (EDGE), two modulation schemes are defined and supported in the base stations and wireless devices. The transmitters in the base stations and the wireless devices need to switch from one modulation scheme to the other whenever there is a need to do so. For example, a first time slot may use Gaussian Minimum Shift Keying (GMSK) modulation and a second time slot may use GMSK or 8 phase shift keying (PSK) modulation and vice versa. The transition from GMSK to 8PSK and vice versa should be smooth to reduce the creation of frequency spikes due to switching. In other words, phase discontinuity when the modulation switching occurs should be minimized to reduce the creation of high frequency interference.